Inhaled vaccines could be better at curbing Covid spread: Experts
But safety and efficacy of such vaccines must still be proven in clinical trials, say experts
Covid-19 vaccines that are administered through the nose or mouth could potentially be more effective in blocking the virus at the upper respiratory tract and thus reduce its transmission, said infectious disease experts in Singapore.
But the safety and efficacy of such vaccines still have to be proven in clinical trials, they stressed.
The experts were commenting on Covid-19 vaccines delivered through ways other than injection, after China's drug authority last week approved an inhaled vaccine co-developed by CanSino Biologics for clinical trials.
Inhaled or intranasal vaccines that are sprayed into the nose mimic the way respiratory viruses usually infect a person - by entering the respiratory tract.
These vaccines are expected to induce a strong local immune response in the upper respiratory tract, where the Sars-Cov-2 virus takes hold.
"This local immune response is therefore potentially more effective at blocking the pathogen immediately when the virus is inhaled or comes into contact with the nose," said Associate Professor Sylvie Alonso, co-director of the Infectious Diseases Translational Research Programme at the National University of Singapore's Yong Loo Lin School of Medicine.
There may be a higher chance of reducing human-to-human transmission when the pathogen is effectively neutralised immediately or soon after it starts replicating, she said.
Injectable Covid-19 vaccines that have been approved so far - such as the Pfizer-BioNTech and Moderna shots - have been shown to prevent disease, but have yet to show conclusively that they can reduce transmission.
Professor Ooi Eng Eong from the emerging infectious diseases programme at Duke-NUS Medical School said the theoretical benefits of intranasal and inhaled Covid-19 vaccines are uncertain without efficacy trials.
These vaccines are in the exploratory stages of testing, noted Prof Ooi, the co-developer of an injectable Covid-19 vaccine that is to undergo phase three trials in the second quarter of this year.
China is not the only place where intranasal Covid-19 vaccines are being studied.
OXFORD UNIVERSITY
Last Thursday, Britain's Oxford University said it was launching a study of immune responses of a nasal administration of its vaccine developed with AstraZeneca.
In Singapore, home-grown biotech company Esco Aster is working with United States company Vivaldi Biosciences to develop a vaccine that will be delivered as a nasal spray.
Prof Alonso said that as the nasal cavity is close to the brain, developers must ensure that the components of the vaccine cannot reach the brain.
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